Exchange 2007 missing a lot of updates. What is best approach to update with least risk?

We are in the process of looking at moving from Exchange 2007 to Exchange 2013, but the Exchange 2007 server we have is seriously behind on updates for reasons beyond our control until now. I note that for any Exchange 2007 to 2013 upgrade (different hardware) the 2007 server must be on:
"Update Rollup 10 for Exchange 2007 Service Pack 3 (SP3) on all Exchange 2007 servers in the organization, including Edge Transport servers."
and the 2013 server must be on:
"Exchange 2013 Cumulative Update 2 (CU2) or later on all Exchange 2013 servers in the organization."
The 2013 is not going to be an issue as it is not built yet, but our current 2007 is on "Update Rollup 8 for Exchange Server 2007 Service Pack 1  8.1.375.2  5/19/2009 KB968012" Whereas the current (recent) update (patch, SP) for Exchange 2007 is: Update Rollup 19 for Exchange Server 2007 Service Pack 3  8.3.459.0 3/14/2016  KB3141352
We are thus 2 SP and multiple KB updates behind.
We need to patch that server (single Exchange with no failover or load balance - mission critical), but what would be the best approach.
Do we try to install each Service Pack individually and then the updates/rollups, hence SP1 -> SP2 -> SP3 + 10 rollups, etc... or since these are cumulative can we just try to install Service Pack 3 (skip SP1 and SP2) and the extra rollups, i.e.

Microsoft Exchange Server 2007 SP3      8.3.083.6      6/20/2010      
Update Rollup 1 for Exchange Server 2007 Service Pack 3      8.3.106.2      9/9/2010      KB2279665  

Update Rollup 2 for Exchange Server 2007 Service Pack 3      8.3.137.3      12/10/2010      KB2407025  

Update Rollup 3 for Exchange Server 2007 Service Pack 3      8.3.159.0      3/2/2011      KB2492691  

Update Rollup 3-v2 for Exchange Server 2007 Service Pack 3      8.3.159.2      3/30/2011      KB2530488  

Update Rollup 4 for Exchange Server 2007 Service Pack 3      8.3.192.1      7/7/2011      KB2509911  

Update Rollup 5 for Exchange Server 2007 Service Pack 3      8.3.213.1      9/21/2011      KB2602324  

Update Rollup 6 for Exchange Server 2007 Service Pack 3      8.3.245.2      1/25/2012      KB2608656  

Update Rollup 7 for Exchange Server 2007 Service Pack 3      8.3.264.0      4/16/2012      KB2655203  

Update Rollup 8 for Exchange Server 2007 Service Pack 3      8.3.279.3      8/13/2012      KB2734232  

Update Rollup 8-v2 for Exchange Server 2007 Service Pack 3      8.3.279.5      10/9/2012      KB2756497  

Update Rollup 8-v3 for Exchange Server 2007 Service Pack 3      8.3.279.6      11/13/2012      KB2778154  

Update Rollup 9 for Exchange Server 2007 Service Pack 3       8.3.297.2       12/10/2012       KB2746157  

Update Rollup 10 for Exchange Server 2007 Service Pack 3      8.3.298.3      2/11/2013       KB2788321  

It does get backed up without issues and I have lots of backups. FYI!
Anybody experience any issues with updates.
Single Exchange 2007 (HUB role) without about 400 mailboxes, distribution lists etc, but no public mailboxes.
Laszlo DenesAsked:
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Todd NelsonSystems EngineerCommented:
Neither Exchange 2013 CU2 (Jul 2013) or Exchange 2007 SP3 UR10 (Feb 2013) are not supported by Microsoft.

The only supported Exchange 2013 CUs that are supported are CU12 and CU13. And the only supported Exchange 2007 SP and URs that are supported are SP3 with SP3 UR19 and SP3 UR20.

For the Exchange 2007 server, install the SP3 (only) first and restart. Then install the latest SP3 UR and restart. Then, I would recommend installing all remaining recommended and optional Windows Updates that are available (except .NET Framework 4.6.x).

With the URs, you only need to install the latest as they are cumulative for SP3.  With the CUs, you only need to install the latest.

If you run, Windows Updates on the server hosting Exchange 2007 after you install the most recent UR and it shows previous URs, do not install them.

Also, DO NOT install .NET Framework 4.6.x on any server that will host Exchange.  .NET FX 4.6.x is only supported on servers hosting Exchange after Exchange 2013 CU13 or Exchange 2016 CU2 have been installed.

https://oddytee.wordpress.com/2014/08/27/exchange-2013-product-version-numbers/
https://oddytee.wordpress.com/2014/08/27/exchange-2007-product-version-numbers/

Additionally, if the global catalog servers (DCs) have not been updated in a long time, I recommend updating those as well. I've seen some mailbox connectiviy issues after moving a mailbox to a new Exchange server if they aren't current.

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Scott CSenior EngineerCommented:
In addition to the above:

Upgrade your servers in the following order:
1.Client Access servers (beginning with the internet-facing site)
2.Hub Transport and Edge Transport servers
3.Mailbox servers
4.Unified Messaging servers
Todd NelsonSystems EngineerCommented:
Laszlo,

Will you provide an update on your progress with updating the Exchange 2007 servers?
Todd NelsonSystems EngineerCommented:
You should have enough information to complete your request successfully.
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